Sorry about that. I was much more sure about the "net" part than the "hack" part, but then the wiki kind of seemed to confirm my guess about why the original "Hack" was called as such: https://nethackwiki.com/wiki/Hack
But rereading it now, it just seems like someone looked up the word "hack" after the fact, and your explanation makes more sense.
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Correction: it wasn't that people were hacking on it, the name 'hack' referred to hacking at monsters.
Sorry about that. I was much more sure about the "net" part than the "hack" part, but then the wiki kind of seemed to confirm my guess about why the original "Hack" was called as such: https://nethackwiki.com/wiki/Hack
But rereading it now, it just seems like someone looked up the word "hack" after the fact, and your explanation makes more sense.